Generally, as shown in FIGS. 1 and 2, a conventional watch chain 100 includes a plurality of outer connection pieces 10 in which a pin hole 11 is formed at a spaced position of each piece so that the left and right sides of each outer connection piece 10 are communicated with each other. The central connection pieces 20 include pin holes 21 formed at spaced portions so that the left and right sides of the central connection pieces 20 are communicated with each other. A pipe shaped or pin shaped connection piece 30 is inserted into the pin hole 11 of the outer connection piece 10 of one side and the pin hole 11 of the outer connection piece 10 of the other side through the pin hole 21 of the central connection piece 20 so as to engage the central connection piece 20 and the outer connection pieces 10. An additional pin 31 is inserted into the pin hole 11 of the side surface of the outer connection piece 10 and is connected with the connection piece 30. The connection piece 30 is inserted into the pin hole 11 of the outer connection pieces 10 and is fixed by the pin 31, and the central connection piece 20 is rotatable with respect to the connection pin 30.
The pin hole 11 of a new outer connection piece 10 is formed at both sides of another pin hole 21 of the thusly engaged central connection piece 20. The connection pin 30 is inserted into the pin hole 11 of the outer connection piece 10 of one side and the pin hole 11 of the outer connection piece 10 of the other side through the pin hole 21 of the central connection piece 20, and the pin 31 is inserted into the pin hole 11 of the outer connection piece 10.
The outer connection pieces 10 and the central connection pieces 20 are alternately engaged using the connection pins 30 and the pin 31, so that the length of the watch chain can be adjusted with a desired length.
However, the above-described conventional watch chain has the following problems. The connection pin and the pin are inserted into the pin hole of the outer connection piece of the other side through the pin hole of the outer connection pin of which left and right sides communicate and the pin hole of the central connection piece of which left and right sides communicate. With this construction, the pin may be escaped from the pin hole of the outer connection piece as the time passes. In the case that a watch chain is made of a certain special material such as ceramic, etc., the pin cannot be stably fixed because the surface of the ceramic material is slippery. In view of the world-class watch fabrication standard, it is impossible to fabricate a watch chain which can meet the watch chain assembling pressure standard. In addition, when viewing the watch chain in a state that the watch is worn on a user's wrist, since the pin holes are seen from the sides of the outer connection pieces, so that the outer look of the watch chain may be damaged. Therefore, the value of the product may decrease.
In addition, when adjusting the length of the assembled watch chain, a specialist for watch should adjust the length of the watch chain using a certain tool such as a hammer, etc.